And this is why protagonists should never be allowed to name things/beings.
Then I believe you are re talking about this one:
http://www.mangago.zone/read-manga/ore_to_kawazu_san_no_isekai_hourouki/
You also have the one when MC purposely give them horrible nickname that they all hate:
http://www.mangago.zone/read-manga/tensei_kyuuketsukisan_wa_ohirune_ga_shitai/
Are you talking about this one?
http://www.mangago.zone/read-manga/the_rhapsody_of_me_and_her/
I don’t remember it well if he/she did tend to mess with people name though XD
On one hand, I’m on her side. But on the other, if someone I sent to get sacrificed came back on the back of a being my country considered a monster and told me she was an envoy from the warring neighboring country who are now in peace out of nowhere, I’d be suspicious as fuck. They should have waited for rumors of peace to spread, sent a messenger with a sealed letter telling of the new ruler and that an envoy would be coming, and then she could have come. Maybe things would have still ended with Lord Greed coming, but at least I could say that only the king was dumb and not Elyanna. She was raised as the future queen, she should know this.